Paper is on the auditory condition tinnitus and possible treatments of varying backgrounds for it.
Assignment 2
Introduction
Tinnitus is a condition that causes the patient to perceive sounds that do not originate externally and affects as many as 50 million Americans, some to the point that their quality of living degenerates.
Although tinnitus is elicited from damage to the ear, new research suggests that it could originate in the brain.
The Three Faces of Tinnitus
The first component of tinnitus is the acoustic component, the unwanted sound that varies greatly from individual to individual, having varying pitches and intensity.
The second component of tinnitus is the attentional component, which deals with how greatly the unwanted noise affects the patient’s quality of life by how well they can focus on other things.
The third and final component of tinnitus is the emotional component, which entails how deeply affected the patient is by condition. This can range from mild annoyance to aggravation to acute depression.
The three components together detail the patient’s condition, as a more intense acoustic component will have a greater effect on the attentional component or a more emotionally-affected individual will thus focus more of their attention on the condition
The Acoustic Component and the Theory of Tinnitus Induction
Alterations to the balance of excitatory and inhibitory inputs of neurons in the auditory system are believed to cause tinnitus.
High-intensity noises that cause hearing loss damage auditory receptions in the inner ear, resulting in hearing loss that alters neuronal activity in the auditory system of the brain, causing tinnitus.
Central Plasticity as a Cause
Several areas of the brain show signs of tinnitus activity, most notably in the dorsal cochlear nucleus where direct input is received from the auditory nerve.
Loss of auditory nerve function results in high rates neural activity in the absence of stimuli.
The brain perceives the increased neural activity as sound, particularly high frequency sound such as the ringing perceived by tinnitus patients.
The inferior colliculus, which receives input from the cochlear nucleus, increases in spontaneous neural activity as a result.
The auditory cortex is also affected, causing neural impulses to synchronize so that impulses occur simultaneously, amplifying tinnitus.
Damage to the ear from noise exposure distorts frequency perception such that the brain becomes insensitive to sound frequencies of the range of hearing loss.
Neurons whose input frequency have been lost alter to become sensitive to noises at the edge of the lost frequencty, resulting in an expansion of the representation of frequencies near that of the hearing loss at the cost of equal representation of the entire range of audible frequencies. This could possibly affect tinnitus.
Neural Basis of Plasticity
Hearing loss throws off the balance between excitatory synapses which increase neural activity and inhibitory synapses that reduce neural activity.
Excitation is necessary for delivering responses to stimuli throughout the brain and enhancing important signals, while inhibition is necessary for turning off response to stimuli to avoid an information overload to the brain.
Hearing loss results in a decrease of auditory inhibition, coupled with an increase in excitatory synaptic response.
Decrease in inhibitory synapses could be responsible for the inability of many tinnitus patients to filter out the tinnitus ringing for other sounds.
Increases levels of acetylcholine have been noted to occur after hearing loss. This could be the brain’s mechanism to boost its ability to perceiving incoming signals.
The resulting amplification allows the neural signals caused by hearing loss to be more easily perceived, thus resulting in tinnitus.
Reversing Plasticity
It has been theorized that hearing can be restored by reversing the plasticity changes made by hearing loss through restoration of sound stimulation to the areas of the brain that have lost input. This restored plasticity should reduce activity that causes tinnitus.
Research has been done to expose animals to loud noise that results in hearing loss. All the changes to auditory responses in the brain detailed above were found to have occurred in the animals.
The same animals were exposed to auditory stimulation in the frequency range of hearing loss and were found to have greatly restored the balance of synapses and reduced the activity of neurons and their synchronization. Acoustic therapies could thus possibly treat hearing loss and tinnitus symptoms.
The Attentional Component
Tinnitus plays on the consciousness of the patient based on the intensity of its frequency, with fairly light tinnitus merely reduced to an annoying background noise while debilitating tinnitus consuming the attention of the patient.
It is thought that those whose tinnitus falls into a lower level of consciousness may possess cortical deafness that prevents the person from deciphering or associating sounds despite being able to perceive them, which in turn keeps the tinnitus from rising high enough in the hierarchy of awareness to pose a notable issue.
Those with remaining function in the auditory cortex suffer from more acute tinnitus due the piercing quality of the noise, which is perceived by the limbic cortex as a disturbance. This causes a negative association to the sound.
The attention to the noise produced by tinnitus can also be traced back to the dorsal cochlear nucleus, inferior colliculi, and the brainstem, as evidenced by cats’ ability to discern noises of varying intensities arriving at the two ears at different times, which requires attention.
Changes in the activity of the dorsal cochlear nucleus in animals when they shift their attention between auditory and non-auditory stimuli suggest the dorsal cochlear nucleus’ role in attention. In addition, it has been shown that the dorsal cochlear nucleus and inferior colliculi function in attention regulation.
Testing with hydranencephaly sufferers who lack of cerebral hemispheres but maintain an intact brainstem has shown these individuals to show interest to certain sounds and respond emotionally to them. This suggests that these low-level auditory centers might serve to enable the brain to focus on specific details in the sensory world and while ignoring those deemed irrelevant.
The auditory cortex assists the auditory centers to analyze sounds and interpret them. It can be surmised that disturbances to lower auditory areas can be responsible for both causing tinnitus and dictating the amount of attention focused on the tinnitus.
The Emotional Component
Emotional responses are not exclusive to the limbic system, but can be found to occur in the lower brainstem and autonomic nervous system.
Emotional responses to stimuli, such as anxiety, can be found to coincide with activation in the lower brainstem regions such as the locus coeruleus.
The chain of nerve cluster cells distributed along the braistem is responsible for producing serotonin, which can cause depression when inbalanced.
Serotonin is evidenced to be released into the dorsal cochlear nucleus with exposure to loud noises, which plays heavily on the emotional response of the tinnitus patient.
Summary
Understanding the plasticity of the brain and how it alters due to the changes brought about by hearing loss is producing models that allow the explanation of tinnitus, which influences the direction that tinnitus treatments will take.
The developments made into understanding tinnitus have made the thus elusive cure much closer in reach
Paper is on the auditory condition tinnitus and possible treatments of varying backgrounds for it.
Assignment 2
Introduction
- Tinnitus is a condition that causes the patient to perceive sounds that do not originate externally and affects as many as 50 million Americans, some to the point that their quality of living degenerates.
- Although tinnitus is elicited from damage to the ear, new research suggests that it could originate in the brain.
The Three Faces of Tinnitus- The first component of tinnitus is the acoustic component, the unwanted sound that varies greatly from individual to individual, having varying pitches and intensity.
- The second component of tinnitus is the attentional component, which deals with how greatly the unwanted noise affects the patient’s quality of life by how well they can focus on other things.
- The third and final component of tinnitus is the emotional component, which entails how deeply affected the patient is by condition. This can range from mild annoyance to aggravation to acute depression.
- The three components together detail the patient’s condition, as a more intense acoustic component will have a greater effect on the attentional component or a more emotionally-affected individual will thus focus more of their attention on the condition
The Acoustic Component and the Theory of Tinnitus Induction- Alterations to the balance of excitatory and inhibitory inputs of neurons in the auditory system are believed to cause tinnitus.
- High-intensity noises that cause hearing loss damage auditory receptions in the inner ear, resulting in hearing loss that alters neuronal activity in the auditory system of the brain, causing tinnitus.
Central Plasticity as a Cause- Several areas of the brain show signs of tinnitus activity, most notably in the dorsal cochlear nucleus where direct input is received from the auditory nerve.
- Loss of auditory nerve function results in high rates neural activity in the absence of stimuli.
- The brain perceives the increased neural activity as sound, particularly high frequency sound such as the ringing perceived by tinnitus patients.
- The inferior colliculus, which receives input from the cochlear nucleus, increases in spontaneous neural activity as a result.
- The auditory cortex is also affected, causing neural impulses to synchronize so that impulses occur simultaneously, amplifying tinnitus.
- Damage to the ear from noise exposure distorts frequency perception such that the brain becomes insensitive to sound frequencies of the range of hearing loss.
- Neurons whose input frequency have been lost alter to become sensitive to noises at the edge of the lost frequencty, resulting in an expansion of the representation of frequencies near that of the hearing loss at the cost of equal representation of the entire range of audible frequencies. This could possibly affect tinnitus.
Neural Basis of Plasticity- Hearing loss throws off the balance between excitatory synapses which increase neural activity and inhibitory synapses that reduce neural activity.
- Excitation is necessary for delivering responses to stimuli throughout the brain and enhancing important signals, while inhibition is necessary for turning off response to stimuli to avoid an information overload to the brain.
- Hearing loss results in a decrease of auditory inhibition, coupled with an increase in excitatory synaptic response.
- Decrease in inhibitory synapses could be responsible for the inability of many tinnitus patients to filter out the tinnitus ringing for other sounds.
- Increases levels of acetylcholine have been noted to occur after hearing loss. This could be the brain’s mechanism to boost its ability to perceiving incoming signals.
- The resulting amplification allows the neural signals caused by hearing loss to be more easily perceived, thus resulting in tinnitus.
Reversing Plasticity- It has been theorized that hearing can be restored by reversing the plasticity changes made by hearing loss through restoration of sound stimulation to the areas of the brain that have lost input. This restored plasticity should reduce activity that causes tinnitus.
- Research has been done to expose animals to loud noise that results in hearing loss. All the changes to auditory responses in the brain detailed above were found to have occurred in the animals.
- The same animals were exposed to auditory stimulation in the frequency range of hearing loss and were found to have greatly restored the balance of synapses and reduced the activity of neurons and their synchronization. Acoustic therapies could thus possibly treat hearing loss and tinnitus symptoms.
The Attentional Component- Tinnitus plays on the consciousness of the patient based on the intensity of its frequency, with fairly light tinnitus merely reduced to an annoying background noise while debilitating tinnitus consuming the attention of the patient.
- It is thought that those whose tinnitus falls into a lower level of consciousness may possess cortical deafness that prevents the person from deciphering or associating sounds despite being able to perceive them, which in turn keeps the tinnitus from rising high enough in the hierarchy of awareness to pose a notable issue.
- Those with remaining function in the auditory cortex suffer from more acute tinnitus due the piercing quality of the noise, which is perceived by the limbic cortex as a disturbance. This causes a negative association to the sound.
- The attention to the noise produced by tinnitus can also be traced back to the dorsal cochlear nucleus, inferior colliculi, and the brainstem, as evidenced by cats’ ability to discern noises of varying intensities arriving at the two ears at different times, which requires attention.
- Changes in the activity of the dorsal cochlear nucleus in animals when they shift their attention between auditory and non-auditory stimuli suggest the dorsal cochlear nucleus’ role in attention. In addition, it has been shown that the dorsal cochlear nucleus and inferior colliculi function in attention regulation.
- Testing with hydranencephaly sufferers who lack of cerebral hemispheres but maintain an intact brainstem has shown these individuals to show interest to certain sounds and respond emotionally to them. This suggests that these low-level auditory centers might serve to enable the brain to focus on specific details in the sensory world and while ignoring those deemed irrelevant.
- The auditory cortex assists the auditory centers to analyze sounds and interpret them. It can be surmised that disturbances to lower auditory areas can be responsible for both causing tinnitus and dictating the amount of attention focused on the tinnitus.
The Emotional Component- Emotional responses are not exclusive to the limbic system, but can be found to occur in the lower brainstem and autonomic nervous system.
- Emotional responses to stimuli, such as anxiety, can be found to coincide with activation in the lower brainstem regions such as the locus coeruleus.
- The chain of nerve cluster cells distributed along the braistem is responsible for producing serotonin, which can cause depression when inbalanced.
- Serotonin is evidenced to be released into the dorsal cochlear nucleus with exposure to loud noises, which plays heavily on the emotional response of the tinnitus patient.
SummaryKaltenbach JA. Insights on the origins of tinnitus: An overview of recent research. Hearing Journal: 62 (2), 26-29. http://journals.lww.com/thehearingjournal/Fulltext/2009/02000/Insights_on_the_origins_of_tinnitus__An_overview.5.aspx